Various types of movable surface apparatus have been proposed. Such apparatus, often referred to as "treadmills," are suitable for physical exercise and training in sports and physical conditioning; and for physical rehabilitation after accident or disease have stricken a user. Such apparatus usually includes an endless belt or the like, which may be a wide rubber belt supported throughout its width by a stationary support so that the rubber belt will not bow or bend through due to the weight of the user. As the movable rubber band engages a back-up support surface, substantial friction between the rubber band and the support surface arises, requiring substantial drive power. The rubber band is subject to wear due to friction between it and the support. The feel of the step on the rubber band is disagreeable since it is hard, because the thickness of the rubber band is limited to restrict the drive power to reasonable levels.
Various types of construction for the surface itself have been proposed, and roller supports have previously been disclosed, see, for example, U.S. Pat. No. 1,016,729, Barrett, of February 6, 1912. Difficulties arise in use when placing roller supports beneath a rubber or fabric blanket, particularly if reinforced, since the drive power to move a heavy blanket which does not transmit the "feel" of the rollers to the user requires considerable drive power while, additionally, the noise level of such apparatus is high. It has also been proposed to utilize chain drives in which the rubber belt or blanket itself is driven and pulled by chains. Again, the drive power is considerable and the noise level is high. In addition lateral forces of the leg of the runner causes belt guiding problems with a high risk of accident. Two guide systems are necessary: a continuous adjustment of the movable surface about the rotable elements in a manner, wherein the position of the step slats is exactly right-angled with regard to the running direction. This is guaranteed by ribs, either attached to the step slats or preferably to the drive belt like a teeth belt. The ribs correspond to the ribber circumference of the driving elements and forces the movable surface into the right position preventing lateral movement and dangerous lock. Another guiding system is located beneath the runner to prevent lateral movement of the movable surface in this area.